Field of the Invention
The invention relates to a weld detection apparatus and weld detection method.
Description of the Background Art
Vehicles such as hybrid vehicles and electric vehicles that have been widespread these days include a power supply that supplies power to a motor and the like that is a power source. The power supply includes an assembled battery made by a plurality of stacked power storage cells. After a voltage output from the power supply is boosted by a voltage boosting circuit connected to the power supply via a switch, such as a system main relay (SMR), the power is supplied to the motor at the voltage.
For example, there is a technology that prevents overcharge of the power supply by redundancy monitoring that monitors a function monitoring overcharge of the power supply based on a voltage used to charge a capacitor connected in series with the power supply in such a configuration. Moreover, for example, a technology that detects an insulation problem and a SMR weld problem of a vehicle based on the voltage used to charge a flying capacitor connected to the power supply, vehicle insulation resistance and a vehicle body earth, has been proposed.
More specifically, since in a case where the SMR is welded, the flying capacitor is charged via a vehicle insulation resistance located further than the SMR from the power supply, whether the SMR is welded can be detected by a process using the insulation problem detection. On the other hand, since, in a case where the SMR is not welded and is normal, an insulation resistance on a side of the power supply is much greater than a vehicle insulation resistance located further than the SMR, the flying capacitor is not charged. Thus, it is possible to detect, based on the voltage of the charged flying capacitor, whether or not the SMR is weld.
However, the foregoing conventional technology cannot eliminate an influence of a smoothing capacitor and the like included in the boosting circuit on charging the flying capacitor. Thus, difference occurs in weld detection for a SMR, i.e., it is not possible to accurately perform the weld detection for the SMR.